The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
A hybrid electric vehicle uses an internal combustion engine and a battery power source together. That is, the hybrid electric vehicle efficiently combines and uses torque of the internal combustion engine and torque of the motor.
In general, the hybrid electric vehicle includes an engine, a motor, an engine clutch selectively connecting the engine to the motor, a transmission, a differential gear device, a high voltage battery, a hybrid starter & generator (HSG) starting the engine or generating power according to output of the engine, and wheels. The HSG may refer to an integrated starter & generator (ISG).
The hybrid electric vehicle provides driving in an electric vehicle (EV) mode in which only torque of the motor is used; a hybrid electric vehicle (HEV) mode in which torque of the engine is used as main torque and torque of the motor is used as auxiliary torque, by engaging or releasing the engine clutch depending on acceleration intention and deceleration intention based on a manipulation of an accelerator pedal and a brake pedal by a driver, a vehicle speed, a state of charge (SOC) of the battery, and the like; and a regenerative braking mode in which braking and inertial energy are recovered through electrical power generation of the motor during braking of the vehicle or during deceleration of the vehicle by inertia to be charged in the battery.
Since the hybrid electric vehicle uses both mechanical energy of the engine and electrical energy of the battery, uses optimal operation regions of the engine and the motor, and recovers the energy upon braking, fuel efficiency may be improved and the energy may be efficiently used.
The engine clutch is engaged or released according to hydraulic pressure applied from a solenoid valve. A hydraulic pressure sensor is used to monitor the hydraulic pressure applied to the engine clutch. The hydraulic pressure applied to the engine clutch may be measured based on a voltage received from the hydraulic pressure sensor. As shown in FIG. 7, there is a linearity error in measured voltages of the hydraulic pressure sensor. We have discovered that if the linearity error of the hydraulic pressure sensor is not properly corrected, it is difficult to control the engagement degree of the engine clutch. Because power performance and fuel consumption of the hybrid electric vehicle are affected by the engagement degree of the engine clutch, a method for learning the linearity error of the hydraulic pressure sensor is requested.